Hydrometallurgical processing of Nd–Fe–B magnets for Nd purification

An evaluation of various metal purification processes subsequent to the leaching processing of the neodymium (Nd) product from neodymium–iron–boron (Nd–Fe–B) magnets has been conducted. These post-leaching purification processes included precipitation; replacement and electrolysis were studied in order to check the purity of the recovered neodymium. A hydrometallurgical investigation was adopted to digest the metal content of the scrap Nd–Fe–B magnets for the recovery of valuable Nd metal and other metals such as Fe, B, Co and Ni. The effect of leaching conditions such as solid-to-liquid ratio and temperature were optimized and 100 % Nd, 100 % Fe, 100 % B and 85.87 % Co leaching efficiencies were achieved under these conditions. The coating material of the magnet, Ni, achieved 50 % impregnation after increasing the reaction temperature to 70 °C. The metals present in the optimal leaching solution were recovered 99 % by pH adjustment. However, the replacement had the highest separation efficiency for the recovery of Nd metal. Further, the optimal leaching Nd–Fe–B solution was subjected to the electrolysis processes in order to verify the recovery efficiency for all metals.     

Control strategies for biohydrogen production by immobilized co-culture of Clostridium butyricum and Rhodopseudomonas palustris

In this study, we evaluated biohydrogen production of Clostridium butyricum and Rhodopseudomonas palustris by immobilized co-culture. Effects of free cells and immobilized cells, immobilized biomass ratio, sucrose concentration, and initial pH on hydrogen production were investigated. The immobilized co-culture can achieve high cumulative hydrogen volume yield (604 mL) as compared to free co-culture cumulative hydrogen volume (513 mL) while the initial sucrose concentration was 17.8 g/L. The optimum C. butyricum/R. palustris ratio was 1:10, yielding the highest cumulative hydrogen (728 mL). High sucrose concentration (above 35.6 g/L) would inhibit hydrogen production. The optimal initial pH value for hydrogen production of immobilized co-culture was 7.0 (cumulative hydrogen volume 830 mL).     

A comparative study on arsenic and humic substances in alluvial aquifers of Bengal delta plain (NW Bangladesh), Chianan plain (SW Taiwan) and Lanyang plain (NE Taiwan): implication of arsenic mobilization mechanisms

Humic substances in groundwater and aquifer sediments from the arsenicosis and Blackfoot disease (BFD) affected areas in Bangladesh (Bengal delta plain) and Taiwan (Lanyang plain and Chianan plain) were characterized using fluorescence spectrophotometry and Fourier transform infrared (FT-IR) spectroscopy. The results demonstrate that the mean concentration of As and relative intensity of fluorescent humic substances are higher in the Chianan plain groundwater than those in the Lanyang plain and Bengal delta plain groundwater. The mean As concentrations in Bengal delta plain, Chianan plain, and Lanyang plain are 50.65 μg/l (2.8–170.8 μg/l, n = 20), 393 μg/l (9–704 μg/l, n = 5), and 104.5 μg/l (2.51–543 μg/l, n = 6), respectively. Average concentrations and relative fluorescent intensity of humic substances in groundwater are 25.381 QSU (quinine standard unit) and 17.78 in the Bengal delta plain, 184.032 QSU and 128.41 in the Chianan plain, and 77.56 QSU and 53.43 in the Lanyang plain. Moreover, FT-IR analysis shows that the humic substances extracted from the Chianan plain groundwater contain phenolic, alkanes, aromatic ring and amine groups, which tend to form metal carbon bonds with As and other trace elements. By contrast, the spectra show that humic substances are largely absent from sediments and groundwater in the Bengal delta plain and Lanyang plain. The data suggest that the reductive dissolution of As-adsorbed Mn oxyhydroxides is the most probable mechanism for mobilization of As in the Bengal delta plain. However, in the Chianan plain and Lanyang plain, microbially mediated reductive dissolution of As-adsorbed amorphous/crystalline Fe oxyhydroxides in organic-rich sediments is the primary mechanism for releasing As to groundwater. High levels of As and humic substances possibly play a critical role in causing the unique BFD in the Chianan plain of SW Taiwan.     

Predicting work performance in nuclear power plants

Diagnosis and monitoring are the major tasks of an operator in main control room of nuclear power plants (NPPs). The operator’s mental workload influences his/her performance, and furthermore, affects the system safety and operations. This study investigated the operator’s mental workload and work performance of the NPP in Taiwan. An experiment including primary and secondary tasks was designed to simulate the reactor shutdown procedure of the fourth nuclear power plant (FNPP). The performance of the secondary tasks (error rate), subjective mental workload (NASA Task Load Index, NASA-TLX) as well as seven physiological indices were assessed and measured. The group method of data handling (GMDH) was applied to integrate these physiological indices to develop a work performance predictive model. The validity of the proposed model is very well with R² = 0.84 and its prediction capability is high (95% confidence interval). The proposed model is expected to provide control room operators a reference value of their work performance by giving physiological indices. Besides NPPs, the proposed model can be applied to many other fields, e.g. aviation, air transportation control, driving and radar vigilance, etc.     

Phylogenetic changes in soil microbial and diazotrophic diversity with application of butachlor

We investigated changes in population and taxonomic distribution of cultivable bacteria and diazotrophs with butachlor application in rice paddy soils. Population changes were measured by the traditional plate-count method, and taxonomic distribution was studied by 16S rDNA sequencing, then maximum parsimony phylogenic analysis with bootstrapping (1,000 replications). The bacterial population was higher after 39 than 7 days of rice cultivation, which indicated the augmentation of soil microbes by rice root exudates. The application of butachlor increased the diazotrophic population in both upper (0–3 cm) and lower (3–15 cm) layers of soils. Especially at day 39, the population of diazotrophs was 1.8 and 1.6 times that of the control in upper and lower layer soils, respectively. We found several bacterial strains only with butachlor application; examples are strains closest to Bacillus arsenicus, B. marisflavi, B. luciferensis, B. pumilus, and Pseudomonas alvei. Among diazotrophs, three strains closely related to Streptomyces sp. or Rhrizobium sp. were found only with butachlor application. The population of cultivable bacteria and the species composition were both changed with butachlor application, which explains in part the contribution of butachlor to augmenting soil nitrogen-fixing ability.     

Formulas of components of citronella oil against mosquitoes (Aedes aegypti)

The mosquito Aedes aegypti is an epidemic vector of several diseases such as dengue fever and yellow fever. Several pesticides are used to control the mosquito population. Because of their frequent use, some mosquitoes have developed resistance. In this study, we used the Y-tube olfactometer to test essential oils of Cymbopogon species and screened specific formulas of components as repellents against Ae. aegypti. At 400 μL, the extracted oil of citronella grass (Cymbopogon nardus) and myrcene produced a low-active response by inhibiting mosquito host-seeking activity. Citronella grass, lemon grass (Cymbopogon citratus), citral and myrcene also produced a low-treatment response to repellents, for more potential to affect host-seeking behavior. Furthermore, the mixture of citral, myrcene, and citronellal oil (C:M:Ci = 6:4:1) greatly affected and inhibited host-seeking behavior (76% active response; 26% treatment response with 40 μL; 42.5%, 18% with 400 μL; and 19%, 23% with 1000 μL). As compared with the result for N,N-diethyl-3-methylbenzamide (DEET; 44%, 22% with 400 μL), adjusting the composition formulas of citronella oil had a synergistic effect, for more effective repellent against Ae. aegypti.     

Persulfate oxidation of trichloroethylene with and without iron activation in porous media

In situ chemical oxidation with persulfate anion (S2O82*) is a viable technique for remediation of groundwater contaminants such as trichloroethylene (TCE). An accelerated reaction using S2O82* to destroy TCE can be achieved via chemical activation with ferrous ion to generate sulfate radicals (SO4*)(E degrees =2.6 V). The column study presented here simulates persulfate oxidation of TCE in porous media (glass beads and a sandy soil). Initial experiments were conducted to investigate persulfate transport in the absence of TCE in the column. The persulfate flushing exhibited a longer residence time and revealed a moderate persulfate interaction with soils. In TCE treatment experiments, the results indicate that the water or persulfate solution would push dissolved TCE from the column. Therefore, the effluent TCE concentration gradually increased to a maximum when about one pore volume was replaced with the flushing solution in the column. The presence of Fe2+ concentration within the column caused a quick drop in effluent TCE concentration and more TCE degradation was observed. When a TCE solution was flushing through the soil column, breakthrough of TCE concentration in the effluent was relatively slow. In contrast, when the soil column was flushed with a mixed solution of persulfate and TCE, persulfate appeared to preferentially oxidize soil oxidizable matter rather than TCE during transport. Hence, persulfate oxidation of soil organics may possibly reduce the interaction between TCE and soil (e.g., adsorption) and facilitate the transport of TCE through soil columns resulting in faster breakthrough.     

Development and implementation of a remote-sensing and in situ data-assimilating version of CMAQ for operational PM2.5 forecasting. Part 1: MODIS aerosol optical depth (AOD) data-assimilation design and testing

This two-part paper reports on the development, implementation, and improvement of a version of the Community Multi-Scale Air Quality (CMAQ) model that assimilates real-time remotely-sensed aerosol optical depth (AOD) information and ground-based PM_2.5 monitor data in routine prognostic application. The model is being used by operational air quality forecasters to help guide their daily issuance of state or local-agency-based air quality alerts (e.g. action days, health advisories). Part 1 describes the development and testing of the initial assimilation capability, which was implemented offline in partnership with NASA and the Visibility Improvement State and Tribal Association of the Southeast (VISTAS) Regional Planning Organization (RPO). In the initial effort, MODIS-derived aerosol optical depth (AOD) data are input into a variational data-assimilation scheme using both the traditional Dark Target and relatively new “Deep Blue” retrieval methods. Evaluation of the developmental offline version, reported in Part 1 here, showed sufficient promise to implement the capability within the online, prognostic operational model described in Part 2. In Part 2, the addition of real-time surface PM_2.5 monitoring data to improve the assimilation and an initial evaluation of the prognostic modeling system across the continental United States (CONUS) is presented.

Implications: Air quality forecasts are now routinely used to understand when air pollution may reach unhealthy levels. For the first time, an operational air quality forecast model that includes the assimilation of remotely-sensed aerosol optical depth and ground based PM_2.5 observations is being used. The assimilation enables quantifiable improvements in model forecast skill, which improves confidence in the accuracy of the officially-issued forecasts. This helps air quality stakeholders be more effective in taking mitigating actions (reducing power consumption, ride-sharing, etc.) and avoiding exposures that could otherwise result in more serious air quality episodes or more deleterious health effects.     

Utilization of polymerase chain reaction and selective media cultivation to identify Legionella in Taiwan spring water samples

In this study, we investigated the distribution of Legionella in sources of spring water and wastewater throughout Taiwan. Legionella were detected with culture method and PCR method from water samples, combined with molecular methods that allow the taxonomic identification of Legionella species. Factors associated with the distribution of Legionella including the physical?Cchemical and microbiological water quality characteristics were also measured. Legionella were detected in 18 of the 68 samples. Additionally, 16 of the 68 samples analyzed by polymerase chain reaction (PCR) and eight of the 68 samples evaluated using the culture method were found to be positive for Legionella. The Legionella species identified included Legionella pneumophila, unnamed Legionella genotypes, uncultured Legionella spp., and Legionella lytica. Legionella species were found in water with temperatures ranging from 10.0 to 50.6??C and with pH values ranging from 5.59 to 9.32. Significant differences (Mann?CWhitney U test, P?<?0.05) were observed in the presence/absence of Legionella in samples with different pH values when Legionella were detected by the culture method. The results of this survey confirmed that Legionella is ubiquitous in the water of spring recreational areas in Taiwan. Long-term investigations of the occurrence of Legionella in hot spring recreational areas throughout Taiwan are needed.     

Methane emissions from free-ranging cattle: comparison of tracer and integrated horizontal flux techniques

Accurate measurements of methane (CH4) emission rates from livestock in their undisturbed natural environments are required to assess their impacts on radiative forcing (i.e., enhanced greenhouse effect) and the environment. Here we compare results from two nonintrusive techniques for the measurement of CH4 emissions from cattle. The cows were kept in an outdoor feeding strip that allowed them to follow natural behavioral patterns but contained them within a well defined space. In the first technique, nitrous oxide (N2O) was released as a tracer at the upwind edge of the feeding strip, and the downwind concentrations of N2O and CH4 were measured simultaneously using Fourier transform infrared (FTIR) spectroscopy. Average CH4 emission per cow was calculated each half-hour on three separate days from the correlation between the two gases. The second technique was the integrated horizontal flux (IHF) or 1-D mass-balance method, in which we used the measured vertical profiles of CH4 concentration and windspeed downwind of the cows to determine the total CH4 emission. Comparing the IHF results to the known release rate of N2O allowed us to test the IHF technique independently. We found agreement within 10% for all comparisons on all days. The daily CH4 emission rate averaged over all tracer and IHF measurements was 342 g CH4 head(-1) d(-1). This is within the range of previous measurements for mature lactating dairy cattle (200-430 g CH4 head(-1) d(-1)) but higher than expected for yearling cattle. The high CH4 emissions are accompanied by high CO2 emissions determined from the FTIR measurements. The bias is most likely due to the measurements being made during and after supplementary feeding of the cattle.